Disk drives are an important data storage technology based on several crucial components including disk media surfaces and read-write heads. When in operation, rotation of disk media surfaces, with respect to the read-write heads, causes each read-write head to float a small distance off the disk media surface it accesses. However, for a variety of reasons, disk media surfaces frequently stop rotating when not in operation for awhile.
When the disk media surface is not rotating with respect to the read-write head, mechanical vibrations acting upon the disk drive can cause the read-write head to collide with the disk media surface, unless they are separated.
This separation is often referred to as “parking” the read-write heads. Parking the read-write heads minimizes the possibility of damaging the disk media surfaces and/or the read-write heads due to these mechanical collisions. Often such parking mechanisms include a ramp on which the head slider(s) are “parked” and a latch mechanism. The purpose of the latch mechanism is to minimize the chance that the actuator will accidentally leave the parking ramp outside the disk media surface and potentially damage the disk media surface(s).
FIG. 1A illustrates a typical prior art high capacity disk drive 10 including actuator arm 30 with voice coil 32, actuator axis 40, suspension or head arms 50-58 with slider/head unit 60 placed among the disks.
FIG. 1B illustrates a typical prior art high capacity disk drive 10 with actuator 20, actuator arm 30 with voice coil 32, actuator axis 40, head arms 50-56 and slider/head units 60-66 with the disks removed.
Since the 1980's, high capacity disk drives 10 have used voice coil actuators 20-66 to position their read/write heads over specific tracks. The heads are mounted on head sliders 60-66, which float a small distance off the disk drive surface 12 when in operation. Often there is one head per head slider for a given disk drive surface. There are usually multiple heads in a single disk drive, but for economic reasons, usually only one voice coil actuator.
Voice coil actuators are further composed of a fixed magnet actuator 20 interacting with a time varying electromagnetic field induced by voice coil 32 to provide a lever action via actuator axis 40. The lever action acts to move head arms 50-56 positioning head slider units 60-66 over specific tracks with remarkable speed and accuracy. Actuator arms 30 are often considered to include voice coil 32, actuator axis 40, head arms 50-56 and head sliders 60-66. Note that actuator arms 30 may have as few as a single head arm 50. Note also that a single head arm 52 may connect with two head sliders 62 and 64.
While there are many forms of mechanical impact upon a disk drive, only rotary shock in actuator 30's plane of motion can bring the read-write heads into collision with disk media surfaces once the read-write heads are parked. These rotary shocks will be described herein based upon a view defining clockwise and counterclockwise rotations with respect to the disk drive base, with a parking zone located to the right of the disk media surfaces as viewed from above the disk base. As will be apparent to one of skill in the art, it is just as possible for a disk drive to use a parking zone on the left of the disk media surfaces. While this is most certainly possible, the discussion hereafter will focus on a parking zone to the right to clarify the discussion. Such a clarification is not meant to limit the scope of the claims.
FIG. 1C illustrates a magnetic latch affixed to an actuator arm 30 of the prior art.
A magnet is affixed to the tail end of the voice coil 32 region, which when near a second magnet located in either the top yoke or bottom yolk of the fixed magnet region 20, will tend to attract actuator 30 to a parking site often inside the disk media. Magnetic latches are used with Crash Start Stop (CSS) designs.
While they have been put into production in several circumstances, they place additional requirements on the voice coil actuators. This kind of latch requires additional actuator torque to exit from the parking zone. Further, these latches require sophisticated actuator speed control. Inside disk parking zones also tend to heat the read-write heads more. The read-write heads tend to suffer more frequent mechanical collisions with the disk surface.
The outside disk surface approach to parking read-write heads parks the read-write head or heads on a ramp outside the disk surface, removing and/or minimizing the possibility for contact when the disk is not in operation. Latch mechanisms provide at least some assurance that the actuator will remain parked with head sliders on the ramp even after mechanical shocks to the disk drive.
FIGS. 2A to 2C illustrate the operation of a single lever inertial latch as found in the prior art.
FIG. 2A illustrates the prior art single level inertial latch mechanism including latch arm 100 pivoting about 102 and including latch hook 104, mechanically fitting with actuator catch mechanism 106, as well as latch stop 110, and crash stop 90, with the latch mechanism at rest.
Note that actuator 30 abuts crash stop 90 and that inertial latch arm 100 abuts latch stop 110 when the single-lever inertial latch is at rest. Slider 60 is in position on parking ramp 120.
FIG. 2B illustrates the prior art single level inertial latch during a clockwise acceleration of actuator 30.
In a clockwise acceleration, actuator 30 moves away from crash stop 90 and actuator catch mechanism 106 engages with inertial latch catch mechanism 104.
FIG. 2C illustrates the prior art single level inertial latch during a counterclockwise acceleration of the actuator.
In a counterclockwise acceleration, the latch may fail if the actuator 30 rebounds from its crash stop 90.
FIG. 3A illustrates a prior art example of a dual-lever inertial latch at rest.
When at rest, a magnet or spring, (which are not shown), biases the small latch arm 142 clockwise, holding the latch 144-152 open.
FIG. 3B illustrates a prior art example of a dual-lever inertial latch during a clockwise rotational acceleration of actuator 30.
FIG. 3C illustrates a prior art example of a dual-lever inertial latch during a counterclockwise rotational acceleration of actuator 30.
The large latch arm 140 rotates in opposite directions during the clockwise and counterclockwise motions of actuator arm 30 of FIG. 3B and 3C, respectively. Motion of large latch arm 140 in either direction causes the small arm 142 to rotate counterclockwise to the close position. This dual lever action prevents a rebound of actuator arm 30 off the crash stop 90 from escaping the latched condition.